The optical pickup device included in disc players for use with optical discs for signal recording or reproduction comprises a base movable radially of the disc, a lens holder carrying an objective lens and supported on the base shiftably in the focusing direction and tracking direction, electric coils mounted on the lens holder, and permanent magnets arranged on the base and opposed to the coils. The position of the objective lens relative to the optical disc is adjusted with respect to the above two directions by passing control current through the coils, whereby a beam emanating from the objective lens is focused on the signal bearing surface of the disc and caused to trace the signal track on the surface.
Unexamined Japanese Patent Publication SHO 63-244325 discloses such an optical pickup device. With reference to FIG. 6 showing the disclosed device, six yokes 101 are provided upright on a base 100. The four outer yokes are each provided with a permanent magnet 102 opposed to the inner yoke adjacent thereto, with a magnetic gap formed between the magnet 102 and the inner yoke. A focusing coil 103 and tracking coils 104 are arranged in the magnetic gaps with a clearance formed around each coil. These yokes 101, permanent magnets 102 and coils 103, 104 constitute a magnetic actuator, above which an objective lens 105 and a lens holder 106 are disposed. The coils 103, 104 are fixed to the lens holder 106, which in turn is shiftably supported on the base 100 by means of wires 107, 108.
A cover 109 provided over the magnetic actuator has secured thereto four iron pieces 110 each in intimate contact with the top faces the pair of yokes 101, 101 on opposite sides of the magnetic gap and with the top face of the magnet providing the gap to magnetically connect these members to one another.
With the optical pickup device of FIG. 6, the objective lens 105 is disposed above the magnetic actuator coaxially therewith and gives an increased thickness to the device, making it impossible to compact the device.
Unexamined Japanese Utility Model Publication SHO 59-36030 discloses an objective lens drive device which is similar to the above device in construction and therefore has the problem of a great thickness.
On the other hand, Unexamined Japanese Patent Publication SHO 61-139949 discloses an optical head wherein a lens holder is disposed at one side of a magnetic actuator to position a lens out of alignment with the actuator and thereby give a reduced thickness to the device. Nevertheless, this device has the problem of being larger sideways by an amount corresponding to the size of the lens holder since the holder is merely positioned beside the magnetic actuator which is of the conventional structure.
Unexamined Japanese Utility Model Publication SHO 62-120426 and Unexamined Japanese Patent Publication SHO 63-244325 disclose a pickup and an optical head device, respectively, which are of like construction and have the problem of being large-sized sidewise.
Further when the coils of the optical pickup device are energized for driving the objective lens, the coils produce Lorentz's force, and the yokes or magnets are similarly subjected to Lorentz's force, which is therefore likely to vibrate the yokes and magnets.
However, none of the devices disclosed in the foregoing publications have any means for preventing the vibration of the magnetic actuator, so that the vibration, if delivered to the optical system of the device, will inadvertently vibrate the objective lens, presenting difficulties in reading signals properly.